Insights into Cholera Toxin

Cholera toxin (CT) is the primary toxin produced by Vibrio cholerae. CT consists of an A subunit (CTA) and a B subunit (CTB), where five CTB molecules associate with one CTA through hydrogen bonds and salt bridges, forming a compact and stable AB5 cylindrical hexameric protein complex. CT is recognized as one of the most potent oral immunogens. Oral administration of CT not only induces an immune response against CT itself but also enhances the immune response to co-administered antigens.

Mechanisms of CT's Adjuvant Effects:

Enhanced Intestinal Permeability: CT increases the permeability of the intestinal mucosa, thereby enhancing antigen uptake.

Th2-Dominant Immune Response: CT selectively induces a Th2-biased immune response, promoting the production of specific mucosal IgA antibodies.

Cytokine Modulation: CT significantly elevates IL-4 and IL-5 levels while leaving IL-2 and IFN-gamma levels largely unchanged.

Cholera Toxin B Subunit (CTB)

The A subunit is the active component of cholera toxin, while the B subunit is responsible for receptor binding. The CTB gene sequence is approximately 380 base pairs long, encoding 124 amino acids. Analysis of the CTB amino acid sequence reveals that the first 17 amino acids are highly hydrophobic, forming an alpha helix and a beta sheet. The 21st amino acid, Gly, and Thr are hydrophilic and exposed on the molecular surface, facilitating signal peptide cleavage.

CTB exhibits strong immunogenicity, effectively stimulating the production of mucosal IgA and serum IgG antibodies in the small intestine. It enhances the antigenicity of epitopes and is one of the most widely used mucosal immune adjuvants. CTB promotes antigen passage through mucosal barriers, enhances antigen presentation by dendritic cells (DCs) and other antigen-presenting cells, and increases TGF-beta secretion by heterologous T cells.

CTB binds to ganglioside GM1 on the membranes of nucleated cells. This property allows CTB to be selectively taken up by GM1-rich neurons, making it a specific marker for neuronal tracing.

Applications of CTB:

Immune Adjuvant

Oral Immunization

Development of Cholera Toxin Vaccines

Neuronal Tracing

Membrane Biology Tool - Membrane Organization Probe

Sensing and Inducing Membrane Curvature

Application Examples

Neuronal Tracing

Researchers injected CTB conjugated with Alexa Fluor 488 into the rat gastrocnemius muscle and CTB conjugated with Alexa Fluor 594 into the tibialis anterior muscle to determine the optimal observation time for labeled neurons. Results showed that the best neuronal visualization was achieved 3-7 days post-injection.

Figure 1: Distribution of motor, sensory, and sympathetic neurons labeled with AF488-CTB (Day 3 post-injection).

Immune Adjuvant

Helicobacter pylori Studies: CTB-UE was used as an immunogen for prophylactic and therapeutic immunization experiments. Results demonstrated that CTB-UE induced specific and high-level antibodies against H. pylori.

Figure 2: Multi-epitope vaccine design CTB-UE.

West Nile Virus (WNV) Vaccine Research: Researchers used non-toxic WNV DIII-CTA2/B as an immunostimulant. Mice were immunized with a mixture of DIII-CTA2/B, WNV DIII alone, or CTA2/B alone. Results indicated that DIII-CTA2/B effectively induced specific humoral immunity and promoted isotype switching to IgG2.

Figure 3: Complement-mediated bactericidal assay of immunized mouse serum.

High-Quality CTB Recombinant Protein from UA BIOSCIENCE

We provide high-purity (>95%) recombinant Cholera Toxin B subunit, available for immediate supply.

Cholera Toxin B subunit，1μg on SDS-PAGE under reducing and Non-reducing condition. The purity is greater than 95%.

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